This invention relates to an improved method and apparatus for heating articles up to a limited temperature as fast as possible, consistent with the lack of scorching and damage to the finish of the article and then to cool the article back to the ambient room temperature. The opthalmic profession in particular has use for such a device in fitting of thermoplastic eyeglass frames to the head of an individual person, each being a customized fit.
The background of the opthalmic use shows many devices using heat of conduction, convection and radiation and includes patents in my name such as:
U.s. pat. Nos.
2,789,200 issued Apr. 16, 1957, PA1 3,816,705 issued June 11, 1974, PA1 3,932,114 issued Jan. 13, 1976 PA1 Allowed application Ser. No. 589,200, filed June 23, 1975, now U.S. Pat. No. 4,052,593.
No matter what manner or method is used to accomplish heating it will usually be found to also have dis-advantages as well as advantages. As for instance, with heat of conduction, contact with heated particles leaves impressions on the surface of the article, sometimes with particles themselves embedded in the article. With heat of convection; as in a liquid immersion type, the liquid residue must be wiped and removed. Again with convectional air heating, transfer of heat is quite slow but the article stays clean and needs no further treatment.
When an article is irradiated with infrared rays its color and surface texture effect its absorption of heat energy. Also in this case the wave length of the rays determines how much energy is absorbed, reflected, or passes through that particular article. To expound on this critical area that this invention is concerned with, the following tabulation will make things clear to compare the range of wave length radiation.
__________________________________________________________________________ Microns Microns Microns % of radiant energy absorbed Source 0-2 2-6 6-20 by a typical white surface __________________________________________________________________________ 2500.degree. K. (4073.degree. F.) 60% 35% 5% 30% 1000.degree. K. (1341.degree. F.) 5% 65% 30% 70% 700.degree. K. (800.degree. F.) 5% 45% 50% 85% 600.degree. K. (621.degree. F.) -- 35% 65% 90% __________________________________________________________________________
The above table information was taken from Bulletin PE-70-Corning Industrial Radiant Heaters-Corning Glass Works, Corning, N.Y. This source indicates that in the 0-2 micron column most products absorb little of this energy. In the 2-6 micron column most products absorb 60% of this energy. In the 6-20 micron column most products absorb 90% of this energy.
It becomes obvious that even though a lot more energy is radiated at say 2500.degree. K. a lot less energy is absorbed, and while at 600.degree. K. a lot less energy is radiated, a lot more energy is absorbed. These facts taken with the color and surface sensitivity of articles tell use that again it is clear that we have advantages and disadvantages in each particular range we operate in.
This invention uses a novel means to convert high energy short wave length radiation heating one or more radiators, each radiating at a different wave length.
Since temperature dictates the frequency a body will radiate at, the invention proposes the use of thin perforate or foraminous sheets each absorbing some radiation on its imperforate areas from a primary source but letting primary radiation pass through their perforate areas, thus delivering two or more frequency ranges of radiation to the article being heated.
When more than one perforate radiator is used, the perforate areas and imperforate areas are positioned so that primary radiation heats the first radiator. The primary radiation that passes through its perforations heats the second radiator while both primary source radiation and first radiator source radiation passes through the perforations of the second radiator toward the article. Thus in this instance, three frequencies of radiation hit the article.
The perforate radiators might be 0.015" of an inch thick and because of the material removed from the perforate area they will be the mass equivalent of a sheet only 0.008" of an inch thick. Another example is: if the solid area is 20% with the hole area being 80% and with a wall thickness of 0.017", the equivalent mass would be an imperforate wall thickness of only 0.0034". This small mass heats and cools very fast.
The invention takes advantage of the fast expansion and contraction of this form of radiator to act as a sensor to control the current supplied to the infrared source generator, to maintain a constant energy output.
By placing all these parts in close proximity to each other a thin compact efficient unit is assemblied which allows placing the article very close to the heating sources.
By addition of a flow of air through this unit the additional advantage of convection heating is obtained with the bonus of the cooling of the sensor for close, small differential control of the generator's output.
It is, therefore, a prime object of this invention to heat an article with rays of radiation of more than a single wave length range because of the variable acceptability of each article to a particular frequency ray.
Another object of the invention is to have a device that is capable of radiating both far infrared and near infrared and if desired a band or bands of those rays in between.
Further relating to color it is an object to radiate more than one frequency range to make the device more color blind and to accept and heat articles in a wide color range in a more uniform time and faster.
Another object is the use of a single infrared generator and subsequent converter radiators to generate a number of radiation frequency ranges, all activated from a prime infrared generator.
Still another object is to shield the eyes of the user from the intense and harmful shorter wave length radiation of the generator.
A further prime object is to use one of the perforate radiators as a sensor to control the current supply to the generator to limit its energy output.
Another object is to provide a generator, a radiator, a sensor and reflector mounting having the same area of output as the frontal area presented by the article to be heated, to provide an even distribution of radiation and prevent hot spots and loss of unused radiation beyond the article to be heated.
An object of importance is the provision of the generator, the radiators and the sensor all compactly close to each other and in close proximity to the article to be heated.
Another object includes the use of moving air passing through the generator, the radiators and the generator support to provide heated air to help heat the article.
A further object is to use a generator, radiator and sensor of small mass for fast heating and fast cooling of these parts.
A still further object is the use of perforate bimetalic material as a radiator and sensor for control of temperature.